新疆洪古勒楞曼托型铜矿床成因及成矿机理

The Manto-type copper deposits are developed in the Pacific Rim and Tethyan metallogenic domains, but have not been recognized in the Central Asian metallogenic domain. We studied newly discovered Hongguleleng copper deposit which located in the West Junggar area, Xinjiang, is stratabound, and occurred within the volcanic sequence with andesitic to basaltic nature. We propose that the Hongguleleng copper deposit is a Manto-type deposit. Historically, syngenetic versus epigenetic theories have been debated and fundamental studies on metallogenic mechanism have scarcely been carried out for the Manto-type copper deposits. The study focuses on specifying the hydrothermal fluid sources and the ore-forming physico-chemical conditions. Based on systemic work in deposit geology, petrology, petrography, and ore mineralogy, we study the fluid geochemistry, hydrothermal fluid inclusions and mineral chemistry using the advanced geochemistry analysis measures in order to trace the hydrothermal fluid sources and investigate ore-forming physico-chemical conditions and their control on the metal transfer and deposition. The aim of this study is to examine the genesis and metallogenic mechanism and compare it with typical Manto-type copper deposits in Chile. Based on these, a model of the Hongguleleng Manto-type copper deposit could be formed. This study can enrich the theory of the Manto-type copper deposit in the world, but also provide a theoretical basis for the exploration of resources and mineralization potential evaluation in Xinjiang.

曼托型铜矿床在环太平洋和特提斯成矿域均发育，而在中亚成矿域目前未见报道。我们对新疆西准噶尔地区勘探新确立的洪古勒楞铜矿床进行了先期研究，认为该矿床赋存于中基性火山岩中，具有显著的层控特点，属于曼托型铜矿床。曼托型铜矿床成因认识长期存在同生和后生成矿之争，成矿机理研究程度较低。本申请项目以洪古勒楞铜矿床成矿流体来源和成矿物理化学条件为研究主线，采用传统和最新方法相结合的手段，在扎实的野外地质和室内岩相学和矿相学研究基础上，进行成矿流体地球化学、流体包裹体和矿物化学研究，查明成矿流体来源、成矿物理化学条件及其对金属元素迁移、沉淀的控制，确定矿床成因及成矿机理，并与智利典型曼托型铜矿床进行对比，建立洪古勒楞曼托型铜矿床成矿模式。此项研究可丰富世界曼托型铜矿床成矿理论，同时也可为新疆矿产资源勘查和成矿潜力评价提供理论依据。

Manto型矿床是世界重要铜矿床类型，在环太平洋和特提斯成矿域均有发育，但在中亚成矿域未见报道。洪古勒楞矿床是新疆首例Manto型矿床。研究表明，洪古勒楞矿区存在古火山机构，火山活动至少经历了4个火山喷发旋回，火山角砾岩和火山机构断裂系及后期断裂构造叠加形成的高渗透性岩石为矿质沉淀提供了赋矿空间。同位素结果显示，硫化物的δ34S为+0.5-+3.4‰，与硫化物共生的方解石的δ18OSMOW和δ13CPDB分别为+8.94-+16.29‰和-2.01-+1.58‰，黄铜矿的206Pb/204Pb为17.44-17.97，与围岩的206Pb/204Pb比值（18.66-20.96）存在差异，表明矿床的成矿物质和流体主要为岩浆来源，有少量海水和围岩物质的混入。成矿早阶段流体具有较高温（237-289℃）、高氧逸度和高硫逸度特征，矿化较弱，发育斑铜矿和磁铁矿，以浸染状和气孔充填状矿石为主；蚀变矿物成分受全岩成分控制，表现为绿泥石具有均一的Fe/（Fe+Mg）比值（0.42-0.43）和绿帘石具有较低且集中的SrO含量（0.14-0.24 wt.%）；黄铁矿具有高Ni（~0.05wt.%）和低Au（~0.06wt.%）含量特征。成矿晚阶段流体的温度（155-255℃）、氧逸度和硫逸度降低，仅发育少量磁铁矿，但反应的水岩比例升高，寄主岩石结构和矿物形态被破坏，矿化强度增加，以块状、角砾状和脉状矿石为主；蚀变矿物成分受流体成分的影响，表现为绿泥石具有多变的Fe/（Fe+Mg）比值（0.38-0.48）和绿帘石具有较高且分散的SrO含量（0.21-0.40 wt.%）；黄铁矿具有低Ni（~0.02 wt.%）和高Au（~0.1 wt.%）含量。根据上述成果，建立了洪古勒楞Manto型矿床的火山机构断裂系-热液蚀变-矿质沉积就位的三阶段成矿模式。洪古勒楞矿床与世界典型Manto型铜矿床具有相似的成矿过程，但高渗透性岩石和断裂控矿的特征更为突出。项目成果具有理论和实际的双重意义。高渗透性岩石和断裂控矿认识的提出丰富了Manto型矿床成矿理论，而洪古勒楞Manto型矿床的确立和成矿模型的建立为在新疆乃至中亚成矿域寻找该类型矿床提供理论支撑和方法借鉴。